One of the most promising approaches for obtaining very high sensitivity from deep within the body is to use a catheter probe. New catheter probe resonators have been designed and improved with an extended length. Various paramagnetic materials have been also examined for use with these catheters and these have been optimized for sensitivity to oxygen and for maximal SNR. We are presently looking at different polymer coatings for application to surfaces of these probes for reasons of bio-compatibility and oxygen permeability.